Shaped Illumination for Vignetting Compensation in Image Capture
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Solution Overview
Problem
Imaging systems, particularly time-of-flight cameras and machine vision systems, face issues with vignetting, leading to non-uniform signal-to-noise ratios (SNRs) due to varying sensing efficiency across the field of view, which conventional digital image processing cannot effectively address.
Innovation Solution
An illuminator is used to provide illumination with a distribution that compensates for the sensing efficiency variations by increasing intensity at the periphery of the field of view, ensuring uniform SNRs across the image capture system, and the image capture system is designed to be sensitive only to the illuminator's light to minimize the impact of ambient lighting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If digital image processing is used to correct vignetting, then the appearance of the image is improved, but the signal-to-noise ratio deteriorates
Solution Approach 1:
The illumination pattern is pre-configured to compensate for vignetting effects before image capture. The illuminator is designed to provide non-uniform illumination that counteracts the expected light falloff, so that the sensor receives uniform light distribution across the field of view, eliminating the need for post-capture digital correction and preserving signal-to-noise ratio.
Solution Approach 2:
The illuminator acts as an intermediary element between the light source and the sensor. By introducing this intermediate component with a specific optical design, the system achieves uniform illumination distribution without requiring digital processing, thus maintaining high signal-to-noise ratio while correcting vignetting.
2Device complexity
If uniform illumination is provided across the field of view, then the illumination is simple, but vignetting cannot be compensated
Solution Approach 1:
The illuminator is designed with spatially varying illumination characteristics where different regions of the illumination pattern have different intensities. Specifically, the illumination intensity is higher at the periphery and lower at the center, matching the vignetting compensation requirements. This local variation in illumination quality enables effective vignetting correction while maintaining a relatively simple overall device structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach results in image data with substantially uniform SNRs, effectively reducing vignetting and improving image quality in applications like security cameras, 3D cameras, and night vision systems.
Implementation Method 1
An illuminator provides illumination having a distribution shaped to have higher intensity where sensing efficiency of an image capture system is lower
Data Source
Figure 1~2B
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Figure 4~5A
AI summary
A system including an image capture system with a sensing efficiency that varies over a field of view of the image capture system may employ shaped illumination to compensate for the variation in the sensing efficiency. An illuminator may be configured to illuminate the field of view of the image capture system with illumination shaped to have higher intensity where the sensing efficiency is lower, e.g., at the periphery of the field over view. The imaging system may thus provide image data with more uniform signal-to-noise ratios. Image data from an illuminated scene may be manipulated using data from a non-illuminated scene to produce improved image data.